#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define ll long long
#define itr ::iterator
typedef pair<int,int> pii;
const int MAX=1e6;
char last;
char X[MAX];
int ind,size[MAX],par[MAX],Parent[MAX][21];
void Init()
{
}
int get(int u)
{
if(par[u]==u or (X[u]>='a' and X[u]<='z'))
return u;
return par[u]=get(par[u]);
}
void TypeLetter(char L)
{
++ind;
X[ind]=L;
par[ind]=get(ind-1);
size[ind]=size[par[ind]]+1;
Parent[ind][0]=par[ind];
for(int A=1;A<21;A++)
Parent[ind][A]=Parent[Parent[ind][A-1]][A-1];
return ;
}
void UndoCommands(int U)
{
++ind;
par[ind]=get(ind-U-1);
size[ind]=size[par[ind]];
Parent[ind][0]=par[ind];
for(int A=1;A<21;A++)
Parent[ind][A]=Parent[Parent[ind][A-1]][A-1];
return ;
}
char GetLetter(int P)
{
P++;
int cur=ind;
for(int A=20;A>=0;A--)
{
if(size[Parent[cur][A]]>=P)
cur=Parent[cur][A];
}
return X[cur];
}
/*signed main()
{
ios_base::sync_with_stdio(false);
TypeLetter('a');
TypeLetter('b');
TypeLetter('d');
UndoCommands(2);
UndoCommands(1);
cout<<GetLetter(2);
//cout<<ind<<" "<<par[ind]<<"\n";
return 0;
}*/
